Digitising audio
Use case: You have a pile of deeply obscure records, cassettes and CDs that really should be preserved for future generations. You want to archive them, without spending a fortune on equipment or doing a lot of mucking about.
You can do this stuff to completely anal perfectionist levels, or just adequately. In practice, adequately is fine, and this stuff is not hard!
FLAC format is the most common compressed lossless audio format, and is recommended. WAV is lossless and a bit more convenient, but twice the size. If someone offers other lossless formats (ALAC, Monkeys, etc.), that's fine, they're all lossless! Archiving a lossy format like MP3 is only a last resort if you have no original to rip from - always rip to lossless if possible.
16-bit 44.1kHz (CD quality) is quite adequate for archiving. 24-bit 96kHz is really really nice for vinyl, if you're feeling perfectionist.
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What archivists want
An archivist will want:
- the sound files
- who ripped it, when
- images of all packaging and the record itself
- all the details about the record (artist, title, catalogue number, track list and times) - a full MusicBrainz entry will do the job
- all equipment and software used
- notes on any problems with the record or the rip
The Internet Archive has/had an LP digitization project, which is a very comprehensive worked example.
Copyright
This should be obvious, but we'll say it anyway: Do not release your rips onto the net without permission of the copyright holders.
In the case of indie recordings owned by the artist, permission can be quite easy to get - asking doesn't hurt, and frequently they're surprised and pleased anyone cares.
But even if you don't release the rip, it can be good to have a wear-proof digital copy of your old vinyl/cassette favourites.
CDs
The best CD ripper bar none is Exact Audio Copy. It includes codecs to rip as FLAC out the box. This will produce 16-bit 44.1kHz files that are precise bit-image copies of what's on the CD.
EAC is a Windows program, but runs flawlessly on Mac or Linux using Wine.
For archiving, either individual tracks or CD-image-with-cuesheet is fine. Individual tracks are way more convenient for actually listening.
Make sure all the CD information (artist, titles, dates) is correct! EAC uses FreeDB.
The second-best ripper is cdparanoia, which every inbuilt CD reading program in Linux uses. Use Linux if you have a CD in such bad condition that EAC fails - e.g. decayed old blue CD-Rs from the 1990s stress CD rippers to their utmost.
There is no point in preserving CD data in any other resolution than 16-bit 44.1kHz - it's digital data already.
Vinyl
Rip vinyl with Audacity, leaving the archive version as one side at a time. You can cut it into tracks for convenient listening later separately. Audacity can save as FLAC.
For archiving, don't do anything to the recording! No tone controls or compression - just straight to digital for the archive copy. Make sure the sound is as reasonably loud as possible, but DOES NOT CLIP - set peaks to -6dB or -12dB if you're not sure. A bit quiet is better than distorted. You can see the waveform and any clipping displayed in Audacity.
Many audio programs provide "audio restoration" functions that attempt to remove hiss, pops, crackles, and other unintended noise typically associated with vinyl and/or other analogue formats. These are useful for later restoration, but just record the archive version unprocessed.
USB turntable
ION does a line of cheap and popular USB turntables. These are 100% better than nothing. Many, many vinyl nerds have one.
They include a USB sound interface at 16-bit 44.1kHz, so you can plug them straight into your computer, where they will appear as a new audio input device. You can then use this as an input in Audacity.
The turntable also includes RCA input plugs which are good for hooking a cassette deck to (so you're just using the device as a sound card).
Your old hifi
Really good turntables are cheap these days. Your old hifi turntable through your old hifi amp with a fresh needle will give good results.
Hifi turntables usually have RIAA-equalized outputs. This means you must run it into a "phono" input. If you don't have one, run it through a phono pre-amplifier (even a cheap $20 one will do) or a hifi amplifier with a phono input and a normal output.
Compact "midi" systems from the 1980s were crappy then and they're crappy now. If someone won't let a rare record out of their hands and only have one of these, they may be a last resort.
Audiophile ideal
Get a sound card that does 24-bit 96kHz, and run a hifi turntable into it (through a phono input). Archivists will love you.
Laser turntable
Got $10,000? (Does anyone know anyone, or any institution, who's actually got one of these?)
Cassettes
Old hifi tape decks are cheap too. Nakamichi is reputedly the best brand, but at this stage anything "hi-fi" is fine. ION also do a cheap USB tape deck, which will do an adequate job. Crappy '80s midi systems are actually less than cassette quality, and are only a last resort.
Digitising at more than 16-bit 44.1kHz is frankly not worth the effort - the noise floor (10-bit) and frequency range (10kHz) of cassettes is well within these limits.
Don't forget to correctly set tape type (ferrous I, chrome II or metal IV) and Dolby B (usually applicable). Apart from this, just archive unprocessed, as with vinyl. Rip a side at a time with Audacity.
If you have a USB turntable, the RCA plug inputs are ideal for this job. If you don't, get a computer sound card with RCA plug inputs.
The sound will benefit from clean tape heads. Do not use abrasive "cleaning tapes" - use isopropyl alcohol (any "tape head cleaner" fluid; isopropanol is cheap on eBay) and a cotton bud on the heads and metal capstans, and a cotton bud dipped in water on the rubber roller. Leave to dry. Wet-clean cassettes (e.g.) are also suitable and low on fuss.
The professional archivist will want to do stuff like align the heads, degauss, etc. If you're just preserving a pile of your ancient tapes, the mere fact of getting it archived and preserved is almost certainly the most important issue.
Really dodgy old tapes may shed oxide the way some old reels do. This is unpredictable in any given pile of tapes. Just make sure each run is your best shot (and clean the heads afterwards).
DAT
There's a lot of these floating around from the 1990s - typically demo or live tapes. They should still be readable 10-20 years later. Check the DAT player is in good condition.
DATs are 16-bit 44.1kHz or 48kHz. If at all possible, just copy the digital data. (If, for some reason, all you can get is analogue, get the highest resolution at the highest bitrate you can.)
Reel-to-reel
Not just master tapes, but old reel-to-reel local band demos for radio stations and so on - public radio stations have or had large boxes of these.
Many of these will be old enough to be decaying - tape is not a durable medium. Sometimes recovering reels is a one-play deal, as that one play will destroy the tape - if you have any doubt, seek specialist help!
There's also the basic "something to play it on" problem ...
The limit of a really good analogue source is 20-22 bits of resolution (even though 10-14 bits is more realistic), so if you're going to go to the effort of recovering old reels then the 24/96 sound card would be a good idea too.
PC sound card or USB audio?
If you don't have a good sound input, some people recommend USB sound interfaces over sound cards - a decent USB interface is a lot cheaper than a high-end sound card, and avoids a lot of earthing and interference issues. Firewire sound interfaces cost a bit more but are really nice. Also, you can use USB/Firewire with a laptop if that's all you have.
This is an area where there's no upper limit on the money you can spend, ranging up to rack mount equipment that will cost you hundreds or even thousands of dollars for each audio channel for a top quality Analog to Digital Converter (ADC). For example, the Apogee Rosetta 200, which runs around $1500-$2000 for two channels of 192kHz, 24 bit conversion. Quality of conversion does make a difference, a better piece of equipment will do a better job at the same sample rate, but when going from relatively low fidelity sources is probably pointless overkill. "Adequately" is actually good enough.
Gotchas
There are several software packages/hardware mixers that by default will mix the two input channels into two identical mono output channels! Check your setup - make sure that the left channel is panned hard left, and the right channel is panned hard right.
